The multilayer sheets are used for making tube as well as pouches for paste, cream, gel and powder products that are sensitive to moisture and oxygen. Generally, a multilayer laminated sheet comprises an outside thermoplastic layer, a barrier layer and inner thermoplastic layer.
Traditionally, a metal foil such as aluminum foil is used as a barrier layer. However, a barrier layer of metal foil with lower gauge (below 20 micron) has more number of pin holes causing poor gas barrier. Moreover, metal foil is susceptible to flex cracking causing further deterioration of barrier properties. Presently, polyethylene terephthalate (polyester), polyamide (PA), Ethylene Vinyl Alcohol (EVOH) polymers are used as barrier layers. However, a barrier layer of polyethylene terephthalate (polyester), polyamide (PA), are suitable for only medium barrier (more than 10 cc/m2) application. Further, though EVOH is a good barrier, it needs minimum thickness (10 micron or more) to achieve effective gas barrier.
Further, a common greater disadvantage of presently available multilayer sheets is in reprocessing and recycling as these multi layer sheets are made of dissimilar polymers and polymer with metal foil.